Many projection display systems use a single light modulator in combination with a white light source to produce a full color image. In order to produce a full color image, the white light source is filtered sequentially to produce a primary colored light beam that changes over time. Typically, a color wheel is used to allow a series of primary-colored filters to be spun through the white light beam in rapid succession. As each filter passes through the light beam, the light beam becomes a primary color beam with the active primary color determined by the portion of the color wheel that is passing through the optical path.
During each primary color period, data for the appropriate color is provided to a spatial light modulator to enable the modulator to create a series of single color images. If the single color images are created in a rapid sequence, the viewer's eye integrates the series of images to give the perception of viewing a single full-color image.
In the past, in addition to three primary colors, color wheels with an additional segment that is clear is used to allow white light to pass directly through the wheel and be combined with the primary colors. These clear segments are often referred to as white segments. White segments are generally utilized to increase the brightness of the resulting image.